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42

6

502 50 18-01

A

Cylinder and piston

The cylinder and the piston are two of the compo-
nents exposed to most strain in the engine. They must
withstand, for example, high speeds, large tempera-
ture swings and high pressure. Moreover, they must
be resistant to wear. Despite these tough working
conditions, major piston and cylinder failure is rela-
tively uncommon. The reasons for this include new
coatings in the cylinder bore, new types of oil and
grease and refined manufacturing techniques.

When servicing these components, cleanliness is of
the utmost importance. It is therefore recommended
that the cylinder and the area around it be thoroughly
cleaned before being dismantled from the crankcase.

Remove the circlips from the gudgeon
pin.

Using long-nose pliers remove the
gudgeon pin circlips.

Keep your thumb over the circlip to
prevent it from flying out.

Dismantling

Dismantle the following components to make the cylinder accessible:

Starter, cylinder cover, muffler guard, muffler and spark plug.

NOTE!

The throttle need not be removed to dismantle the cylinder and piston.

Loosen the clamp (A) and unscrew the bolt a good distance (to facilitate the coming
assembly) so that the clamp can be turned around the inlet manifold without
affecting the cylinder.

Then loosen the 4 bolts holding the cylinder.

Carefully lift out the cylinder by twisting is backwards and forwards until it loosens
from the inlet manifold. Make sure that no dirt enters the crankcase.

Use a rag to cover the crankcase opening under the piston.

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Содержание 343F

Страница 1: ...Workshop manual 343R 345RX 343F 345FX 345FXT English ...

Страница 2: ...__ 3 2 Electrical system _________________________ 7 3 Fuel system _____________________________ 15 4 Centrifugal clutch ________________________ 31 5 Angle gear ______________________________ 37 6 Cylinder and piston ______________________ 41 7 Crankshaft and crankcase_________________ 51 8 Tools___________________________________ 59 Copyright Husqvarna AB Sweden 2003 ...

Страница 3: ...arefully Make sure that ventilation is good when handling petrol trichlo roethylene and other highly volatile liquids The engine exhaust is poisonous Test run the engine only if ventilation is good Preferably outside Special tools Certain tasks in this handbook require the use of special tools In sections where this is applicable an image of the tool with an ordering number is provided We recommen...

Страница 4: ...3 1 1 Contents Dismantling _________________________________ 4 Assembly __________________________________ 5 Replacing the drive dogs ______________________ 6 Starter ...

Страница 5: ...olt in the centre of the starter pulley Lift the starter pulley carefully from the starter cover Loosen the spring tension Loosen the spring tension Pull out the starter cord about 30 cm Brake the starter pulley with your thumb and lift the cord as illustrated Let the starter pulley rotate backwards slowly Dismantling Remove the starter from the engine Dismantling Remove the 4 bolts and lift off t...

Страница 6: ...lace the washer in place and tighten the bolt Attach the new starter cord Push it in to the starter pulley s track as illustrated and then out through the cord guide in the starter cover Make sure that the knot at the end of the cord is as small as possible NOTE New starter cords can be attached without dismantling the starter Anchor the cord in the starter handle Thread the cord through the start...

Страница 7: ...urn the starter pulley anti clockwise 7 revolutions Check the spring tension With the cord completely pulled out the cord pulley should be able to be turned at least another half revolution Mount the starter onto the engine Mount the starter onto the engine Pull out the starter cord a little Place the starter in position and release the starter cord at the same time Check that the ignition cable i...

Страница 8: ...____________________ 8 Replacing the spark plug cover ________________ 10 Dismantling ________________________________ 11 Drive dogs _________________________________ 12 Assembly _________________________________ 12 Heated handles_____________________________ 12 ...

Страница 9: ...heck the electrode gap It should be 0 5 mm Adjust the gap as needed to the correct value with the side electrode If the electrodes are worn more than 50 the spark plug should be changed If the electrodes are worn more than 50 the spark plug should be changed Too large a spark gap entails a great deal of stress on the ignition module and risk for short circuiting Check if a spark occurs when attemp...

Страница 10: ...ther in the stop switch or the short circuit cable Change the switch as needed and check to see if the cable insulation is damaged Still no spark Check other cables and connections Still no spark Check other cables and connections for poor contacts dirt corrosion cable breakage and damaged insulation Make sure that the cables are correctly drawn and lie in the cable grooves Do not forget to check ...

Страница 11: ... 3 Attach the ignition coil to the ignition cable and ensure that the wire is folded along the cable 4 Pull the ignition coil into the spark plug cover NOTE It is important that the tip of the ignition coil hits the centre of the ignition cable to prevent sparking Adjust the air gap Adjust the air gap as needed to the correct value Loosen the bolts Position the feeler gauge and press the ignition ...

Страница 12: ...move the starter cylinder cover and spark plug Attach piston stop no 502 54 15 01 Dismantling Remove the starter cylinder cover and spark plug Fit piston stop no 502 54 15 01 in the spark plug hole NOTE Place the piston stop so it is caught between the piston and the cylinder head Not so it sticks out into the exhaust port Remove the ignition module and the generator Dismantle the ignition module ...

Страница 13: ... damaged Remove the bolts the hooks and the springs Mind the washer A so as not to lose it Replace damaged parts Assemble in the reverse order Check that the hooks can be turned freely when the bolts are tight Electrical system NOTE Do not pry off the heating element before the locking catch has been removed The element can be damaged The heating element in the throttle is accessed when the thrott...

Страница 14: ... bolt that holds the left grip on the handle Pull out handle from the handlebars and then the cables carefully and one at a time so that the steel wire does not loosen from the cables The heating element is located in a pocket in the outside of the handle Use flat nose pliers to pull out the heating element from the handle NOTE Do not pull the cables or their connections Connections can be easily ...

Страница 15: ...14 2 Electrical system ...

Страница 16: ...____ 17 Fuel filter __________________________________ 17 Fuel pump _________________________________ 18 Carburettor ________________________________ 18 Assembly _________________________________ 24 Carburettor settings _________________________ 25 Throttle ___________________________________ 27 Fuel system ...

Страница 17: ...move the air filter B The nylon filter comes in two models The standard filter has a mesh size of 80µ There is also a 44µ unit available There is also a flock filter also as an accessory WARNING Do not clean not the filter with petrol Hazardous Separate the filter halves and clean the nylon filter in warm soapy water The R variant has a foam rubber filter The air filter comes apart Separate the tw...

Страница 18: ...at the cover D over the dia phragm falls off Blow the filter C clean and the sintered filter E with compressed air and mount the fuel cap in the reverse order to how it was disassembled Make sure that the flat surface on the cover D is turned towards the dia phragm Impregnate the filter with air filter oil Impregnate the filter with air filter oil Tip Place the filter in a plastic bag and pour abo...

Страница 19: ...as far as possible into the fuel hose and that the O ring is sufficiently tight so that the filter cannot slide off the tube Fuel pump The fuel pump facilitates cold starts The pump cannot be repaired and must be replaced if it stops working Note how the fuel hoses are connected to simplify assembly Fuel pump The fuel pump has the task of facilitat ing the start of the engine when cold The pump fi...

Страница 20: ...arburettor housing s contact face Default carburettor settings H 1 revolution open L 1 revolution open The carburettor needles are fitted with movement limiters caps The carburettor s design The carburettor can be divided into three different functional units the metering unit the blending unit and the pump unit The metering unit The needles and the fuel control functions are located here The carb...

Страница 21: ...e carburettor Carefully remove the control dia phragm A and gasket B Check the diaphragm for holes and wear on the pin C Replace the diaphragm if required The pump unit Pumps fuel from the tank to the carbu rettor The pump unit This is where the pump diaphragm E that pumps fuel from the tank to the carburettor s measuring unit is found The diaphragm is affected by pressure variations in the engine...

Страница 22: ... bolt and remove the lever arm axle needle valve and spring Remove the pump diaphragm Check the diaphragm for damage Remove the fuel screen and clean it or attach a new one Remove the bolt holding the cover over the pump diaphragm Lift off the cover A the gasket B and the diaphragm C Check the diaphragm for damage to the valve tongues If the valve tongues are bent the pump will not function in a s...

Страница 23: ... for wear Replace if required Remove the valves and dampers If these components are worn idling is disrupted Always replace the valves and dampers at the same time Remove the movement limiters from the jet needles using flat nose pliers Unscrew the jet needles Do not lose the small washers A Lift off the plastic and rubber guides NOTE Note how the jets are positioned For example the H needle is a ...

Страница 24: ... be read from the outside Replace the fuel screen if it is damaged or cannot be cleaned Place the pump diaphragm closest to the carburettor housing Then the gasket and cover and the other compo nents in reverse order of removal Assembling the carburettor Blow the carburettor housing clean Fit a new plug Fit a new main jet NOTE Check that the valves are turned correctly and that they close complete...

Страница 25: ...the carburettor into place Connect the fuel hose A to the carburettor Connect the fuel hose B to the carburettor and make sure that it is in the groove C Place the filter holder in place and make sure that the fuel hose D is under the carburettor and is not pinched Connect the throttle cable E to the carburettor Screw down the filter holder and attach the air filter Attach the various parts of the...

Страница 26: ...king hours Thereafter the carburettor should be fine tuned The default setting is H 1 revolution open L 1 revolution open Carburettor settings Function The carburettor has the task of supplying a combustible fuel air mixture to the cylinder The amount of this mixture is controlled by the throttle The mixture s composition of fuel and air is controlled by means of the adjustable H and L needles WAR...

Страница 27: ...a CARB EPA approved engine adjustment must be carried out according to the instructions below The combiguard or trim guard must be fitted when adjusting the H needle Low speed jet L Find the highest idling speed by slowly turning the low speed needle clockwise and anticlockwise When the highest speed has been found turn the L needle 1 4 turn anticlockwise High speed jet H The high speed H needle a...

Страница 28: ...lockwise Then turn the L needle back a quarter turn Carburettor adjustment 345RX FX Adjusting the H needle 1 Mount the Trimmy Fix 4 wires and use 3 3 mm smooth cord The cord length should be 160 mm measured from the end of the cord to the cord bushing on the trimmer head 2 Run the engine warm for about 5 minutes 3 Turn the H needle so that the highest speed is attained 4 Reduce the speed by 400 rp...

Страница 29: ...bolts B and C Carefully separate the two halves of the throttle Check for wear on pins A and B Replace the throttle control C and lever arm D if necessary Check that the cables are properly pressed into the cut outs E and that the throttle cable F is in the right groove If necessary attach it with silicon adhesive in order to facilitate assembly Check that the protective bellows G are whole and th...

Страница 30: ...er to check if replacement is necessary The stop switch can also be disassem bled now and replaced if necessary Use a screwdriver to press the stop switch s wing locks E Tip Reassembly of the throttle easier if a thin steel wire is wrapped around the handle and bolt F in order to hold the throttle cable and short circuit cables in place Fuel system ...

Страница 31: ...30 ...

Страница 32: ...31 4 4 Contents Dismantling ________________________________ 30 Assembly _________________________________ 32 Clutch drum _______________________________ 32 Centrifugal clutch ...

Страница 33: ... so that the engine can idle without the cutting equip ment s drive shaft rotating Dismantling Dismantle the cable protector loosen bolts A and B Dismantling The clutch is located between the fuel tank and the engine In order to be accessible the tank and handle holder must be moved forward on the shaft 1 Dismantle the cable protector 2 Loosen bolts A and B Move the fuel tank so far forward that t...

Страница 34: ...nd remove the 3 bolts Lift off the front cover plate and the clutch shoes NOTE Do not lose the sleeve bearings found in the clutch shoes Twist apart the clutch Twist apart the clutch Clean and inspect the different parts with regard to wear or other damage Clean and inspect the different parts with regard to wear or other damage Wear on the clutch shoes must not be greater than shown in the illust...

Страница 35: ...nd the remaining parts in the reverse order as set out for dismantling Clutch drum Dismantle the clutch housing and the clutch drum and drive axle from the shaft Clutch drum Separate the engine body and shaft as described previously Loosen the bolts holding the clutch housing against the shaft Remove the clutch housing and drive axle from the shaft Unscrew the clutch drum from the drive axle Unscr...

Страница 36: ...sing if necessary Change the bearings in the clutch housing if necessary Remove the circlip and push out the bearings with a suitable punch and hammer Dismantling is easier if the clutch housing is heated to about 110 C Assemble in the reverse order as set out for dismantling ...

Страница 37: ...36 ...

Страница 38: ...37 5 5 Contents Dismantling ________________________________ 36 Assembly _________________________________ 37 Shaft _____________________________________ 38 Angle gear ...

Страница 39: ...down the engine s high speed to better suit the lower speed a saw blade or trimmer requires to work efficiently Second the angle gear contributes to the saw opera tor s working stance so that it is comfortable and at the same time efficient The power from the engine via the drive axle shall in other words be angled so that the cutting equipment works parallel to the ground Remove the circlip and w...

Страница 40: ...gear in the reverse order as set out for dismantling Fit the bearings on their respective axles It is easier if the bearings are heated to approx 100 C NOTE Do not forget the circlip holding the bearing on the input axle Make sure the bearings bottom in their seats Heat the gearbox to approx 150 C and first lift the output axle in position and then the input axle Make sure the bearings bottom in t...

Страница 41: ...the plastic sleeve B and the O ring C using a knife and pull the drive axle guide out from the shaft When replacing the axle guide the replacement must be inserted into the shaft so that the distance is the same to the two ends of the shaft When fitting a new O ring must be used To avoid damage from the sharp edges of the slits in the gearbox the following assembly procedure is recommended 1 Place...

Страница 42: ...3 Inlet manifold ______________________________ 44 Cleaning inspection _________________________ 44 Assembly _________________________________ 44 Analysis and actions _________________________ 45 Service tips ________________________________ 49 Wear tolerances ____________________________ 50 Cylinder and piston ...

Страница 43: ...efore being dismantled from the crankcase Remove the circlips from the gudgeon pin Using long nose pliers remove the gudgeon pin circlips Keep your thumb over the circlip to prevent it from flying out Dismantling Dismantle the following components to make the cylinder accessible Starter cylinder cover muffler guard muffler and spark plug NOTE The throttle need not be removed to dismantle the cylin...

Страница 44: ...heck with pressure gauge 531 03 06 23 Pump up a vacuum of 50 kPa The valve must be fully tight Otherwise replace the valve NOTE When the valve is fitted the small hole must face outwards Clean the decompression valve and check that the valve head is not dam aged burnt and that the valve oper ates easily If necessary grind the valve with fine grained valve grinding compound Clean the decompression ...

Страница 45: ...e carefully with not too sharp a tool so as not to damage the soft aluminium parts Cylinder and piston Assembly Lubricate the gudgeon pin s needle bearing with a few drops of engine oil and fit the piston Assembly Lubricate the gudgeon pin s needle bearing with a few drops of engine oil Direct the arrow on the top of the piston towards the exhaust port Press in the gudgeon pin and fit the circlips...

Страница 46: ...r as set out for dismantling Analysis and actions Experience tells us that piston or cylinder failure due to manufacturing errors are extremely rare The reason is usually due to other factors which is evident from the following Note the reasons for the breakdown repair the damage and take the actions required to prevent the same thing happening again Small to medium size scores primarily in the mi...

Страница 47: ... ratio 1 33 3 or 1 25 4 The piston ring starts to stick or is completely stuck in its groove and has therefore not been able to seal against the cylinder wall which has resulted in further intensive temperature increases in the piston Seizure scores along the entire piston skirt on the inlet and exhaust sides Action Change the fuel Change to a fuel with the correct oil mixture Correct the carburet...

Страница 48: ...es on the piston s inlet side caused by a broken roller retainer Deep irregular grooves caused by a loose circlip Shown here on the piston s inlet side Piston ring guide pin vibrated loose A too high engine speed can cause the ends of the piston ring to hammer against the guide pin when the piston ring moves in its groove The intensive hammering can drive out the pin through the top of the piston ...

Страница 49: ... dust and dirt from carbon like deposits on the top of the piston and in the piston ring groove The piston ring sits firmly in the groove Piston material has been worn away The lower part of the piston skirt is thinner on the inlet side than on the exhaust side Larger softer particles that penetrate into the engine cause damage to the piston skirt under the piston ring as the illustration shows Ca...

Страница 50: ...luminium disappears With deep seizure score marks the piston and cylinder should be replaced Replace the cylinder and piston Carefully polish the damaged area using a fine file of fine grade emery cloth Before the piston is refitted the cylinder should be polished as above With deep score marks the piston and cylinder should be replaced Carefully loosen the piston rings and clean the groove well b...

Страница 51: ...luminium appears Max 1 0 mm with the piston ring inserted in the lower part of the cylinder Max 1 6 mm Clean the groove before checking the measure ment Max 0 15 mm Clean the groove before checking the measure ment Piston ring play Piston ring groove Piston ring gap Cylinder bore ...

Страница 52: ...ismantling ________________________________ 52 Inspecting the crankshaft _____________________ 54 Assembly _________________________________ 55 Leakage testing the crankcase_________________ 56 Crankshaft and crankcase ...

Страница 53: ...necting rod is exposed to large acceleration and retardation forces as it moves between the top and bottom dead centres This puts special demands on the bearings that must withstand quick changes in load Moreover the bearing s roller retainer must also cope with high tempera tures and friction It is therefore extremely important when servicing to check the roller retainer for cracks wear and disco...

Страница 54: ...ves Fit tool 502 52 39 01 as illustrated Push out the crankshaft from the crankcase half Push out the crankshaft from the crankcase half Remove the bearing and sealing rings from the crankcase halves Heat the crankcase halves to approx 150 C using a hot air gun Knock the halves against a wooden block so that the bearings fall out of their seats Remove the gaskets with a suitable punch ...

Страница 55: ... Also check that the gap is not too great Inspect the sealing rings The seal edge shall be sharp or slightly ground Crankshaft and crankcase Inspect the small end of the connecting rod Inspect the small end of the connecting rod If seizure marks or discolouration are found in the bearing track the crank shaft must be replaced Inspecting the crankshaft Inspect the large end of the connecting rod In...

Страница 56: ...h a few drops of engine oil and position the crankshaft in the clutch side crankcase half Pull the crankshaft into place with tool no 502 50 30 19 Make sure that the connecting rod is not squeezed against the crankcase Fit a new gasket to the clutch side crankcase half Pull the other crankcase half into position and tighten the 4 crankcase bolts Fit a new gasket to the clutch side crankcase half P...

Страница 57: ...l and press the sealing rings until level with the crankcase using a suitable punch or tool 502 50 30 19 The metal covers of the sealing rings should face outwards Assemble the remaining parts in the following order 1 Cable guide and heat guard on the carburettor side of the crankcase 2 Protective grating on the underside of the crankcase 3 Piston and cylinder 4 Partition on the carburettor side w...

Страница 58: ...e mixture irrespective of the speed and workload The carburet tor s adjustable needles have been fitted with movement limiters to prevent the engine from being run with a too rich fuel air mixture Also see the Fuel system chapter Husqvarna E Tech In 1996 Husqvarna presented a new improved two stroke engine as a part of the company s efforts to produce engines that emit smaller amounts of hazardous...

Страница 59: ...58 ...

Страница 60: ..._______________ 60 Fuel system _____________________________ 60 Centrifugal clutch _________________________ 60 Angle gear ______________________________ 61 Cylinder and piston ________________________ 61 Crankshaft and crankcase __________________ 61 Workshop equipment ______________________ 61 ...

Страница 61: ... 50 06 01 502 54 15 01 502 51 94 01 531 00 60 76 502 50 83 01 501 60 02 03 502 21 58 01 502 54 15 01 502 52 16 02 502 11 46 03 505 38 17 09 502 50 18 01 502 50 18 01 502 50 18 01 505 38 13 08 Electrical system Fuel system Centrifugal clutch Starter Fuel system List of tools 8 ...

Страница 62: ...03 55 22 01 502 51 03 01 502 71 14 01 502 50 65 01 503 97 64 01 503 80 17 01 502 52 42 01 531 03 06 23 502 50 70 01 502 50 18 01 505 69 85 70 101 64 23 48 503 26 70 01 502 50 18 01 Angle gear Cylinder and piston Crankshaft and crankcase Workshop equipment List of tools 8 ...

Страница 63: ...2003W24 114 01 98 26 ...

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